What can I use instead of UNION SQL?

What can I use instead of UNION SQL?

When a UNION is required to put together data from multiple queries, you might be able to use a CASE statement instead. This is very useful, particularly when the data for each of the queries in the UNION come from the same table.

Is there UNION in MySQL?

Description. The MySQL UNION operator is used to combine the result sets of 2 or more SELECT statements. It removes duplicate rows between the various SELECT statements. Each SELECT statement within the UNION operator must have the same number of fields in the result sets with similar data types.

Is UNION faster than join?

Union will be faster, as it simply passes the first SELECT statement, and then parses the second SELECT statement and adds the results to the end of the output table.

Can we use join instead of UNION in SQL?

Both Joins and Unions can be used to combine data from two or more tables. The difference lies in how the data is combined. Joins combine data into new columns. If two tables are joined together, then the data from the first table is shown in one set of column alongside the second table’s column in the same row.

How do I merge two queries in SQL without UNION?

You need to create two separate queries and join their result not JOIN their tables. Show activity on this post. JOIN and UNION are differents. In your query you have used a CROSS JOIN operation, because when you use a comma between two table you apply a CROSS JOIN.

How do you avoid a union in SQL?

Avoid the use of the WHILE LOOP. Use UNION ALL instead of UNION whenever is possible. Avoid using the joins of multiple tables in the where and join in the from clause.

Can we join 3 tables in MySQL?

It is possible to use multiple join statements together to join more than one table at the same time. To do that you add a second INNER JOIN statement and a second ON statement to indicate the third table and the second relationship.

How do I merge rows in MySQL?

To merge rows in MySQL, use GROUP_CONCAT().

Will UNION remove duplicates?

UNION removes duplicate rows. UNION ALL does not remove duplicate rows.

Does UNION slow down query?

A Union combines the results of two or more queries, however a UNION also verifies if there are duplicate values and removes them in the query results. If you did not know, that aspect can slow down a query. If possible, we always try to avoid it.

Which join is equivalent to UNION?

Using the JOIN clause, we combine the attributes of two given relations and, as a result, form tuples. Whereas we use the UNION clause when we want to combine the results obtained from two queries. They both combine data differently.

Is Outer join same as UNION?

Answers. Union is vertical – rows from table1 followed by rows from table2 (distinct for union, all for union all) and both table must have same number of columns with compatible datatypes. Full outer join is horizontal.

How can I join two tables without joining?

How to Join Tables in SQL Without Using JOINs

1. Using a comma between the table names in the FROM clause and specifying the joining condition in a WHERE.
2. Using UNION / UNION ALL .

Can we join 2 tables without common column?

There are few ways to combine the two tables without a common column including Cross Join (Cartesian Product) and UNION. This is not a join but can be useful for merging tables in SQL.

Can you Union 3 tables in SQL?

Using JOIN in SQL doesn’t mean you can only join two tables. You can join 3, 4, or even more! The possibilities are limitless.

How do I merge 3 tables in SQL?

How to join 3 or more tables in SQL

1. Simple Join. First, all the tables are joined using the JOIN keyword, then the WHERE clause is used: FROM Employee e JOIN Salary s JOIN Department d. WHERE e. ID = s. Emp_ID AND e.
2. Nested Join. The nested JOIN statement is used with the ON keyword: SELECT e. ID, e. Name, s. Salary, d.

How do I combine multiple rows into one in SQL?

You can concatenate rows into single string using COALESCE method. This COALESCE method can be used in SQL Server version 2008 and higher. All you have to do is, declare a varchar variable and inside the coalesce, concat the variable with comma and the column, then assign the COALESCE to the variable.

How do I merge columns in MySQL?

1. CONCAT. This function is used to concatenate multiple columns or strings into a single one.
2. CONCAT_WS. The CONCAT_WS() function not only adds multiple string values and makes them a single string value.
3. Using them in WHERE CLAUSE. You can use both of them in WHERE CLAUSE for selection based on condition.
4. Conclusion.

Why is UNION all faster than UNION?

Because the UNION ALL operator does not remove duplicate rows, it runs faster than the UNION operator. The following are rules to union data: The number of columns in all queries must be the same.

Which is better UNION or UNION all?

UNION ALL is faster and more optimized than UNION. But we cannot use it in all scenarios. UNION ALL with SELECT DISTINCT is not equivalent to UNION.

Is union efficient in sql?

UNION ALL is faster than UNION because plain UNION is expecting that within two joined datasets are duplicates which need to be removed. If you can ensure (by inner WHERE clauses) that there will be no duplicates, it’s far better to use UNION ALL and let database engine optimize the inner selects.

How do I optimize a union query in MySQL?

Optimize Queries With MySQL Query Optimization Guidelines

1. Avoid using functions in predicates.
2. Avoid using a wildcard (%) at the beginning of a predicate.
3. Avoid unnecessary columns in SELECT clause.
4. Use inner join, instead of outer join if possible.
5. Use DISTINCT and UNION only if it is necessary.

How do I merge two tables in SQL?

Multiple tables can be merged by columns in SQL using joins. Joins merge two tables based on the specified columns (generally, the primary key of one table and a foreign key of the other). Below is the generic syntax of SQL joins. USING (id);

Which join is similar to UNION?

Using the JOIN clause, we combine the attributes of two given relations and, as a result, form tuples. Whereas we use the UNION clause when we want to combine the results obtained from two queries. They both combine data differently. The format of the result that they obtain also varies.

How can I get data from two tables in SQL without joining?

You could try something like this: SELECT FROM ( SELECT f1,f2,f3 FROM table1 UNION SELECT f1,f2,f3 FROM table2 ) WHERE …